Also, for situations where I think there is no question that a qualifier should be used, such as historic population values, have we decided how specific of a property should be used for that qualifier? If we just have a generic date property, that allows growth to happen the fastest, because there are many places that property could be used as a qualifier. I think a date associated with a population value is pretty self-explanatory, but perhaps there are situations where people will be confused as to why there is a date associated with a value. Do we just put information in the property description or create more specific properties to use as qualifiers?
> Date: Thu, 4 Apr 2013 15:02:37 +0200
> From: benedix@zedat.fu-berlin.de
> To: wikidata-l@lists.wikimedia.org
> Subject: Re: [Wikidata-l] Page history and properties
>
> There was a discussion about this months ago and I think that the
> conclusion was every property should have a valid_from and a valid_to
> field [default = end of the universe].
>
> So you can get snapshots for past versions without any magic.
>
> An example for a hypothetic cashflow-database (dates are YYMMDD ) might be:
>
> select * from cf where origin = "wmde" and v2 = 999999 and payment_date
> >= 130404; -- would give the actual view of future cashflows coming
> from wmde
>
> select * from cf where origin = "wmde" and v2 = 121231 and payment_date
> >= 130404; -- would give the view of cashflows coming from wmde seen by
> end of year 2012
>
>
> I don't know if something like this would be easy to add to your
> existing database scheme.
>
> Lukas
>
>
> Am Do 04.04.2013 09:47, schrieb Daniel Kinzler:
> > On 03.04.2013 23:23, Bináris wrote:
> >> A good question from huwiki:
> >>
> >> When I click on an earlier version of the page in the history, will the
> >> "then-value" of the property be shown or the current value?
> >> If I read the 2013 version of [[United States of America]] in 2018, will Obama
> >> be the president?
> > You will see the current value, not the old one. This is the same as for
> > templates and images. A "time warp" system that allows us to view old versions
> > of pages exactly as they were has long been discussed, but is tricky, especially
> > when templates (or, in the case of wikidata, properties) get deleted or renamed.
> > Nobody has come up with a good solution yet.
> >
> > The qualifiers Sven mentioned will allow us to record who was president when in
> > Wikidata, but when including the "current president" on a Wikipiedia page, this
> > will always be the present one, even when looking at old version of the page.
> >
> > -- daniel
> >
>
>
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